Question

What is mass defect and binding energy?

Answer 1

Hint: Think about the term binding energy, it refers to the energy that is required to bind two entities. Here, the nature of the two entities is defined by the fact that these two terms are from a nuclear physics background. Now try to relate mass and energy to determine what mass defect may mean.

Complete answer:
> Mass defect:
When we measure the weight of any atomic nucleus, it is observed that the measured weight will always be slightly less than that of the calculated weight which is obtained by the sum of masses of all protons and neutrons present in the nucleus. This difference in the observed and theoretical weights is known as the mass defect.
> Binding energy:
Binding energy refers to the energy that is required to separate sub-atomic particles or crystal lattices from each other. In this context, we will be talking about protons and neutrons. A system that is bound together typically has a lower energy than free-floating particles.
These terms are said to be related in a way that the mass defect is considered to be the binding energy. The difference in the observed weight and the calculated weight is accounted for by the binding energy. It is a bit difficult to intuitively guess how energy having mass works so we use the following formula to facilitate the conversion:
$$E=m{c}^2$$
This formula is used to calculate the binding energy of each nucleus using the mass defect as they are seen to be equivalent. Einstein proved that this conversion is possible in his special theory of relativity.

Note: Please do not confuse these terms with the ones in crystal lattices. Although crystal lattices have binding energy too, no mass defect is found in them. Hence, we will assume that this question talks about the nuclear and sub-atomic aspect of both these terms.